PREFACE 



The present report upon the trilobites of the Niagaran 

 limestone of the Chicago area is issued as Part II of Bulletin IV 

 of the Natural History Survey of the Chicago Academy of 

 Sciences, Part I of the same Bulletin being a description of the 

 crinoids, published in 1900. In the preparation of the different 

 parts of this Bulletin, no attempt is being made to follow the 

 zoological order of sequence of the different groups of fossils, 

 and the next class to be studied will probably.be the Brachi- 

 opoda. 



In the preparation of the present paper, the collections 

 preserved in the Walker Museum of the University of Chicago 

 have furnished most of the material, although the Egan collection 

 in the museum of the Academy of Sciences has been freely 

 drawn upon, as well as the collections of the Field Museum of 

 Natural History. 



The writer is under especial obligation to Mr. L. H. Hyde, 

 formerly of Joliet, Illinois, but now of Pipestone, Minnesota, 

 -and to Messrs J. H. Handwerk and J. H. Ferris, of Joliet, for 

 many important specimens. These gentlemen have collected 

 extensively in the rock excavated from the Chicago drainage 

 -canal, and have secured much valuable material from near 

 Lemont. Without the material furnished by them the paper 

 would have been far from complete. The specimens used for 

 illustration from their collections have been generously parted 

 with and are now preserved in the collections of Walker Museum. 

 Besides these gentlemen, Mr. G. H. Harris, of Chicago, has 

 presented several important specimens to Walker Museum 

 which have been made use of in the preparation of this paper. 

 Another rich source of valuable material has been the Van Horne 

 collection, recently presented to the Walker Museum by Sir 

 William Van Horne. This collection contains many choice 

 specimens from the Niagaran limestone of northeastern Illinois 

 and southeastern Wisconsin, which have lent great assistance 

 in the study of the trilobites of this region. 



Most of the species which are here described are known to 

 actually occur in the limestones of the Chicago area, but a few 

 have been seen only from Wisconsin. These species, Harpes 

 telleri, Dicranopeltis nasuta and D. telleri, were all collected by 

 Mr. E. E. Teller, of Milwaukee, and are now in his collection. 



